AIO_READ(3) manual page
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aio_read - asynchronous read
#include
<aio.h>
int aio_read(struct aiocb *aiocbp);
Link with -lrt.
The aio_read()
function queues the I/O request described by the buffer pointed to by aiocbp.
This function is the asynchronous analog of read(2)
. The arguments of the
call
read(fd, buf, count)
correspond (in order) to the fields aio_fildes, aio_buf, and aio_nbytes
of the structure pointed to by aiocbp. (See aio(7)
for a description of
the aiocb structure.)
The data is read starting at the absolute file offset
aiocbp->aio_offset, regardless of the current file offset. After the call,
the value of the current file offset is unspecified.
The "asynchronous"
means that this call returns as soon as the request has been enqueued;
the read may or may not have completed when the call returns. One tests
for completion using aio_error(3)
. The return status of a completed I/O
operation can be obtained by aio_return(3)
. Asynchronous notification of
I/O completion can be obtained by setting aiocbp->aio_sigevent appropriately;
see sigevent(7)
for details.
If _POSIX_PRIORITIZED_IO is defined, and this
file supports it, then the asynchronous operation is submitted at a priority
equal to that of the calling process minus aiocbp->aio_reqprio.
The field
aiocbp->aio_lio_opcode is ignored.
No data is read from a regular file beyond
its maximum offset.
On success, 0 is returned. On error, the
request is not enqueued, -1 is returned, and errno is set appropriately.
If an error is detected only later, it will be reported via aio_return(3)
(returns status -1) and aio_error(3)
(error status--whatever one would have
gotten in errno, such as EBADF).
- EAGAIN
- Out of resources.
- EBADF
- aio_fildes
is not a valid file descriptor open for reading.
- EINVAL
- One or more of aio_offset,
aio_reqprio, or aio_nbytes are invalid.
- ENOSYS
- aio_read() is not implemented.
- EOVERFLOW
- The file is a regular file, we start reading before end-of-file
and want at least one byte, but the starting position is past the maximum
offset for this file.
The aio_read() function is available since
glibc 2.1.
POSIX.1-2001, POSIX.1-2008.
It is a good idea to
zero out the control block before use. The control block must not be changed
while the read operation is in progress. The buffer area being read into
must not be accessed during the operation or undefined results may occur.
The memory areas involved must remain valid.
Simultaneous I/O operations
specifying the same aiocb structure produce undefined results.
See
aio(7)
.
aio_cancel(3)
, aio_error(3)
, aio_fsync(3)
, aio_return(3)
,
aio_suspend(3)
, aio_write(3)
, lio_listio(3)
, aio(7)
This page is
part of release 3.78 of the Linux man-pages project. A description of the
project, information about reporting bugs, and the latest version of this
page, can be found at http://www.kernel.org/doc/man-pages/.
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